1. Field of the Invention
The present invention relates to filter elements and filter assemblies, and more particular to coalescing filter element and coalescing filter assembly.
2. Background Information
Advances in diesel engine fuel injection systems have been instrumental in complying with current and future emission standards. Higher pressure fuel produces a finer mist of fuel, which burns cleaner. Common rail injection systems run at higher pressures and allow more injections per combustion cycle improving fuel economy, better engine performance and lower noise. Higher pressure fuel injector systems (e.g., 20,000+ psi) have tighter tolerances and require substantially free water removal to operate at the highest efficiency, and further generally require single-pass free water removal from fuel to minimize wear related failures.
Coalescing filtration can be a highly effective method to remove water from diesel fuels via coalescence, which is generally defined as a process by which two or more droplets, bubbles or particles merge during contact to form a single daughter droplet, bubble or particle. Coalescing filtration is used to separate emulsions into their components and can be classified as a mechanical coalescing unit, which typically use filters or baffles to make droplets coalesce. In contrast, electrostatic coalescing units use direct current (DC) or alternating current (AC) electric fields, or combinations thereof to separate emulsions into their components.
Water is typically introduced into the fuel supply by condensation. Water in a vehicle fuel system can reduce lubricity causing seizure of close tolerance parts and increased wear. Water in fuel storage tanks may cause rust and can promote microbial growth. Microbial growth in fuel storage systems begins in free water at the tank bottom and can quickly migrate through the fuel. In warm weather, microbial “blooms” can quickly overwhelm, and subsequently bypass, fuel filters causing contamination to reach the fuel injectors.
Mobile diesel machines and commercial vehicles are often subjected to the toughest working conditions. Optimum diesel fuel conditioning is particularly important to ensure smooth running of vehicles, and to protect both the engine and the whole drive system from damage. Effective diesel coalescing filtration offers protection from failures, breakdowns and expensive service interventions.
In fluid treatment applications, filtration units include i) disposable units in which the filtration media and housing are integrated into a single use unit, often called “spin-ons” due to a commonly found threaded attachment technique; ii) replaceable units in which the filtration media is formed in an element or cartridge that can be removed from a unit housing forming a filter assembly; and iii) filtration units with cleanable media, such as by back-flushing. Thus a filter element, also called a filter cartridge, within the meaning of this application, is a unit including filter media that is configured to be received in a filter assembly housing. The filter assembly is the filter housing and filter element together with other elements of the unit such as a control, test points, particle counters, bypass valves, etc.
There remains a need for a cost effective, efficient, coalescing filter element and coalescing filter assembly.